Frogs, like most amphibians, excrete solid and liquid waste through an orifice known as the cloaca. Liquid waste enters the cloaca for expulsion through the urinary bladder. Solid waste enters through the colon.
The secretion of solid waste by a frog is the final byproduct of its digestive process. Most frog species have weak teeth and jaw structures that don't allow for effective chewing. Most of what is swallowed by a frog is first broken down in the stomach by muscular forces and the introduction of digestive enzymes. It then moves to the small intestine, where bile and pancreatic juices break the food down further and allow nutrients to be absorbed into the frog's body. Then it moves to the large intestine for the removal of excess water. Finally, it moves through the colon to the cloaca for evacuation.
The liquid waste excreted by a frog consists of water combined with ammonia, urea or uric acid. Nitrogenous substances are filtered from the frog's blood by its renal system, consisting of two kidneys. The waste is channeled through ureters to the urinary bladder where it is amassed and then vented to the cloaca. Aquatic frogs predominantly excrete this nitrogen waste as ammonia, while most land frogs excrete this as urea.